Re: [PATCH 3/4] devicetree: bindings: Add defeature-repeated-start property for Cadence I2C

From: Harini Katakam
Date: Tue Dec 02 2014 - 08:30:51 EST


On Tue, Dec 2, 2014 at 6:46 PM, Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote:
>> But given the bugs, it will be useful to just disable it if the system doesn't
>> require repeated start.
> What do you do when disable repeated start? Sending STOP and START? If
> so, this is really something different than repeated start. By using
> I2C_FUNC_I2C a user expects repeated start, so if the HW does not
> support it, we should say so and don't try to emulate it with something
> different.

Yes, we send stop.
Using repeated start, when number of messages passed > 1, HOLD bit is set
by the driver. This is an indication to the controller not to send a STOP.
If we disable repeated start, the driver will not set HOLD bit.
All the messages are sent but with START and a STOP for each of them.

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